Decoupler with free wheel system and vibration damping and one-way clutch with free wheel system

ABSTRACT

The present invention relates to a decoupler with free wheel system and comprising a vibration damping pulley, a shaft actionable by the pulley, hub pieces having a first hub piece and a second hub piece, hub pieces being mounted between the inner race of the pulley and the outer surface of the shaft, at least one journal element between the shaft and pulley, along with a torsion spring, and a clutch spring, with the first hub piece being mounted on the shaft and the second hub piece being mounted around the shaft and can rotate relative to it, the torsion spring being disposed between the outer race of the hub pieces and the inner race of pulley, having a first end operatively attachable to the pulley and a second end operatively attachable to the second hub piece and the clutch spring being disposed internally in relation to the torsion spring and which is frictionally engaged with the hub pieces for transmission of torque to the shaft.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/238,787 having a filing date of 13 Feb. 2014, which is a nationalstage application under 35 U.S.C. 371 of PCT Application No.PCT/BR2013/000349 having an international filing date of 9 Sep. 2013,which designated the United States, which PCT application claimed thebenefit of Brazil Application No. BR102012022803-3 filed 10 Sep. 2012,the entire disclosure of each of which is incorporated herein byreference.

The present invention relates to a decoupler system with free wheeloperation and a vibration damping mechanism that can be applied tomechanical connections, such as alternators in vehicles. The decouplermechanism according to the invention has a fail-safe system and can alsobe configured to operate as a one-way clutch in a simple way.

DESCRIPTION OF PRIOR ART

Overrunning alternator decouplers (OADs) with a free wheel system areused in some types of drive connections such as electrical alternatorsin automotive vehicles, among others, to enable the transmission ofpower from a drive shaft to a driven shaft, so that the driven shaft canrotate at a faster speed than the drive shaft or in a differentdirection of rotation. In these situations, the decoupler allowsoverrunning between the driving shaft and the driven shaft, providing afree wheel system which allows the two shafts to rotate independently ofeach other. Furthermore, the decoupler also allows to change the naturalresonance frequency of the accessory belt system of an internalcombustion engine, reducing noise and vibration of the system as a wholeand increasing the useful life of some critical components such as thebelt tensioner.

In some torque transmission couplings using a pulley driven by a belt totransmit torque to a shaft, a clutch spring or wrap spring is disposedinside the pulley, in direct contact with the pulley inner race. Theaxle hub or the driven shaft is arranged internally to the clutchspring, so that the clutch spring performs the torque transmissionfunction. In any event, a friction contact between the clutch spring andthe inner surface of the pulley is required so that the driving shaft iscoupled to the driven shaft. This friction involves high levels ofcompression and may cause great wear on the components of the clutch,and in particular on the pulley. To support the high stress levels andto provide acceptable durability of the system, the pulley, andespecially its inner race, must be made of a very resistant material,such as steel, and has to be preferably submitted to a heat treatment toincrease its strength. These requirements increase the weight and costof the decoupler, and require more complex production processes.

In addition, the decoupler mechanism should comprise a torsion spring orother equivalent means which can substantially alter the naturalresonant frequency (as previously mentioned), and thus ensure improvedpower transmission performance. Typically, this spring is disposedinside the clutch spring, between it and the shaft or axle hub. Toprovide the vibrational damping effect, the torsion spring need notexert a contact friction with the other components of the decoupler.However, the larger is the spring, the greater is its strength for therequired level of torque for the application. However, the dimensions ofthe torsion spring are limited by the reduced internal space of theclutch spring.

The document WO2012061936, for example, describes a decoupler which ispositionable between an axis (for example, for an alternator shaft), anda power transmission element (for example, an accessory drive belt) onan engine. The decoupler includes a axle hub that is mounted in thepulley, engaging the power transmission member and a spring thatprovides isolation between the hub and the shaft. The decoupler providesdamping at a preset value between the hub and the pulley. This documentshows the clutch spring in contact with the track on the inside surfaceof the pulley to provide frictional engagement, and the torsion springdisposed internally to the spring clutch, providing vibration damping.

The document WO2012061930, for example, refers to a decoupler assemblyfor use between an axis and an element used to drive the shaft. Thedecoupler includes a pulley, a hub and a coil torsion spring. The twoends of the spring are engageable, at least indirectly, to the pulleyand the hub for the transfer of torque therebetween. At least one end ofthe spring engages an engagement structure (on either the pulley or thehub) that includes a helical axial shoulder and a driver wall. Thespring transfers torque in one direction through the driver wall (forexample, when the pulley rotates faster than the hub), but the end ofthe spring is not fixedly attached to the driver wall. This inventiondoes not allow simultaneous freewheel and anti-vibration damping, norcan any other invention be found in the state of the art showing thesetwo features together, while also using a pulley body of lightweightmaterial.

Another drawback found in the state of the art of decouplers, such asthe previous documents mentioned here, is the occurrence of leakage ofthe grease used to lubricate the clutch spring, torsion spring and otherparts, due to centrifugal force generated when the decoupler is inoperation. As can be seen in the decouplers of the prior art documentscited here, the axle hub or the bearings are usually in direct contactwith the inner race of the pulley, precisely in the region in which thegrease is thrown by centrifugal force. This contact zone between theaxle hub and pulley is not completely leakage-free. Seals may be used toreduce leakage between these parts, but the incorporation of seals meansan additional component to the decoupler assembly, which increases thecomplexity of construction and its cost. In addition, the springs arenot completely isolated within the interior of the decoupler housing,which also contributes to the leakage of grease.

In addition, there are no examples in the prior art of an OAD with afail-safe design which would enable the decoupler to continue to operatefor a period of time, in the case of failure or breakage of the torsionspring. In all examples of previous decouplers, when the torsion springbreaks, the pulley loses all function, failing to transmit torque to thedriven shaft. If the application of the decoupler is on an automotivealternator, the vehicle will only operate until the battery runs out,and then the vehicle will stop completely due to battery dischargebecause the alternator is no longer providing electrical energy.Fail-safe mechanisms would allow the decoupler to continue to operate asif it was a rigid pulley, at least for a period of time, until thedamaged pulley can be replaced.

Finally, the decoupler with an integral free wheel system can operate asfreewheel system only, such as one-way clutches (one-way clutch—OWC)without a vibration absorber system by means of a simple systemadaptation.

OBJECTIVES OF THE INVENTION

A first object of the invention is to provide a decoupler that performsboth free wheel and vibration damping functions, and, in which thepulley can be made of lower strength materials, without surfacetreatments, with low cost and good durability.

Another objective of the invention is to provide a decoupler with atorsion spring of a larger diameter, thereby providing higher torquecapacity in the same space available to the system, thereby minimizingthe potential failure of breakage of the torsion spring if overloaded.This advantage allows the higher torque on the torsion spring withoutthe use of additional components which limit the torque and decrease thetension on the torsion spring.

Another objective of the invention is to provide a decoupler endowedwith simple construction that is waterproof and can reduce greaseleakage due to centrifugal force.

It is also the object of the invention to provide a decoupler with afail-safe mechanism, which allows the assembly to continue to operate,ensuring that the torque continues to be transmitted, even in case offailure or breakage of the torsion spring or clutch spring.

Finally, it is an object of the invention to provide a decoupler thatcan operate as a decoupled OAD as well as a unidirectional clutch, fromsimple modifications to the construction of the assembly.

SHORT DESCRIPTION OF THE INVENTION

The objectives of the invention are achieved by a decoupler with freewheel system and vibration dampening comprising: a pulley, a shaftactionable by the pulley, a axle hub having a first hub piece and asecond hub piece, the hub being coupled between the inner race of thepulley and the outer surface of the shaft, at least one journal elementbetween the shaft and pulley, a torsion spring, a clutch spring, whereinthe first hub piece is coupled in a torsion proof manner on the shaftand the second hub piece is mounted around the shaft and can rotaterelative to it, the torsion spring is arranged between the outer race ofthe hub and the inner race of the pulley having a first end operativelycouplable to the pulley and a second end operatively couplable to thesecond hub piece, and the clutch spring is arranged internally inrelation to the torsion spring and is frictionally couplable to the hubfor transmission of torque to the shaft.

In one embodiment, the second hub piece may have a radial wall extendingradially to the inner race of the pulley, and the first and second hubpieces are disposed with a gap between them.

The clutch spring may be disposed between the external surface of theshaft and the inner surfaces of the axle hub, being frictionally engagedwith the inner surfaces of the hub pieces, or between the outer surfaceof the axle hub and the inner surface of the torsion spring, beingfrictionally engaged with the outer surfaces of the axle hub.

Preferably, the shaft have a first ending region, which fits a portionof smaller inner diameter of the first hub piece, a second endingregion, which interference fits a bearing element, and a center regionwith a smaller outer diameter than the first and the second shaft endingregions.

Preferably, at least one bearing element is mounted between the pulleyand the first axle hub piece. At least one bearing element is mountedbetween the pulley and the shaft, allowing relative rotational movementbetween the pulley and the shaft. The bearing element can comprise atleast one of a roller bearing, a bearing bushing and a bearing ring.

The pulley inner race may comprise a stopper, which fits to the torsionspring first ending and the pulley outer race may comprise a stopper,which fits to the torsion spring second ending when the pulley is inrotational movement. Alternatively, the pulley comprises a first portionwith smaller inner diameter, which extends radially towards the axleshub, and a center portion with greater inner diameter, that makes ahousing cavity side in which is set the torsion spring, this housingcavity side being closed by a grease leakage contention wall formed bythe transition between the pulley smaller inner diameter and the pulleygreater inner diameter, and the axially opposed side is limited by hubsecond piece.

Alternatively, the decoupler comprises a bearing ring mounted to thepulley inner race, and a bearing bushing mounted between the first hubpiece and the bearing ring, wherein the bearing ring has a stopper thatfits the torsion spring first ending when the pulley is in rotationalmovement, and wherein a torsion spring is set inside a housing cavitylimited by the bearing ring in the axial direction and by the hub secondpiece.

Preferably, the housing cavity has an axial length smaller than thetorsion spring axial length, so that the torsion spring disposed insidethe housing exerts an axial force F1 upon the hub second piece, and thehub second piece exerts a friction force Fat at least upon the bearingelement, when the hub second piece rotates relative to the pulley.

Alternatively, the hub second piece has a portion of greater innerdiameter and a portion of smaller inner diameter, providing a cavitybetween the portion of greater inner diameter and the portion of smallerinner diameter, the hub first piece having a portion of smaller innerdiameter, which interference fits on the shaft, and a portion of greaterinner diameter, providing a cavity between the portion of smaller innerdiameter and the portion of greater inner diameter, the cavity providedin the hub second piece being arranged in contiguity with the cavityprovided in the hub first piece, and the clutch spring being set insidethe cavities of the first hub and the second hub.

The first hub piece and the second hub piece have, each, an inner endwith coupling means through which the two hub pieces are coupledtogether. one seal member is optionally (?) positioned on the gapbetween the first hub piece and the second hub piece.

The decoupler may comprise a washer mounted by interference fit with theshaft and extending radially to the pulley, the washer being arranged incontact with a face of the radial wall of the second hub piece, thewasher has a shoulder on its face in contact with the wall, and the wallhas a shoulder on its face in contact with the washer, the wall andwasher are positioned so that the shoulder of the washer is angularlydisplaced relative to the shoulder of the wall, so that when an overloadis applied to the second hub piece, the shoulder of the washer rotatesand overlaps the shoulder of the wall, causing the second hub piece tomove toward the first hub piece and the first and second hub pieces arelocked by interference between them. The shoulder of the washer and theshoulder of the wall each have a thickness of size equal to theclearance between the second hub piece and the first hub piece. Theinner race of the pulley has a recess in the region of contact with theradial wall of the second hub piece and the washer, the recess having aninternal stop which can contact the radial wall, locking the second hubpiece to prevent rotation relative to the pulley only when the shoulderoverlaps the shoulder.

The pulley may be made of steel, aluminum or polymeric materials.

The objectives of the invention are also achieved by a one-way clutchwith free wheel system comprising a pulley, a shaft actionable by thepulley, a hub mounted between the inner race of the pulley and the outersurface of the shaft,

at least one journal element between the shaft and pulley, and a clutchspring frictionally engaged with the hub for transmission of torque tothe shaft, wherein the hub pieces comprises a first hub piece coupled ina torsionproof manner to the axle and a second hub piece rotatablymounted around the shaft, and the first and second hub pieces arearranged with a gap between them, the one-way clutch further comprisinga coupling means between the second hub piece and pulley, the couplingmeans coupling the pulley with the second hub piece with torquetransmission when the pulley rotates in one direction.

The second hub piece preferably has a radial wall extending radially tothe inner race of the pulley, and the inner race of the pulley has aninternal stop which contacts the radial wall (64), locking the secondhub piece in a rotation proof manner relative to the pulley when thepulley rotates in one direction. The objectives of the invention arealso achieved by a decoupler with free wheel system comprising a pulley,a shaft actionable by the pulley, a hub having a first hub piece and asecond hub piece, the hub pieces being coupled between the inner race ofthe pulley and the outer surface of the shaft, at least one journalelement between the shaft and pulley, and a clutch spring frictionallyattachable to the hub pieces for transmission of torque to the shaft,wherein the hub comprises a first hub piece coupled in a rotation proofmanner to the axle and a second hub piece which is rotationally mountedaround the shaft, the second hub piece having a radial wall extendingradially to the inner race of the pulley, the first and second hubpieces being arranged with a gap between them, the decoupler furthercomprising a stop washer mounted by interference fit to the shaft andextending radially to the pulley, the stop washer being arranged incontact with one face of the radial wall of the second hub piece, thewasher has a shoulder on its face in contact with the wall, and the wallhas a shoulder (101) on its face in contact with the washer, the walland washer are mounted so that the shoulder of the washer is angularlydisplaced with respect to the shoulder of the wall, and when an overloadis applied to the second hub piece, shoulder of washer overlaps theshoulder of washer, so that the second hub piece is shifted toward thefirst hub piece and the first and second hub piece are locked byinterference between them.

Preferably, the washer and the shoulder of the wall having a thicknessof size equal to the clearance between the second hub piece and thefirst hub piece. The inner race of the pulley has a recess in the regionof contact with the radial wall of the second hub piece and the washer,the recess having an internal stop which can contact the radial wall,locking the second hub piece in a rotation proof manner to the pulleyonly when the shoulder overlaps the shoulder.

SHORT DESCRIPTION OF THE DRAWINGS

The present invention will, hereinafter, be described in more detailbased on an example of execution represented in the drawings. Thefigures show:

FIG. 1A—is an exploded view of the components of the decoupler accordingto a first embodiment of the invention;

FIG. 1B—is an exploded view of the components of the decoupler accordingto a second embodiment of the invention;

FIG. 2A—is a cross-sectional view of the decoupler shown in FIG. 1A inan assembled state;

FIG. 2B—is a cross-sectional view of the decoupler shown in FIG. 1B inan assembled state;

FIG. 3—is a block diagram schematically showing the internal arrangementof the decoupler in accordance with the invention:

FIGS. 4A, 4B and 4C—are cross sectional views of three methods ofreducing the clearance between the first and second hub componentsaccording to the invention to prevent grease leakage from inside theOne-way Clutch subsystem;

FIG. 5—is a cross-sectional view of the fail-safe mechanism of thetorsion spring and the clutch system of the decoupler, showing thecoupling between the first hub piece, the second hub piece and the stopwasher in the normal operational condition;

FIG. 6—is a cross-sectional view of the fail-safe mechanism of thetorsion spring and the clutch system of the decoupler showing thecoupling between the first hub piece, the second hub piece and the stopwasher operating in the fail-safe mode;

FIGS. 7A and 7B—are the detailed cross sections of the coupling betweenthe second hub piece and the stop washer in the normal and fail-safemodes, respectively;

FIG. 8—shows the wall face of the second hub piece with the hub shoulderfor operation in the fail-safe mode;

FIG. 9—shows the face of the stop washer in contact with the wall of thesecond hub piece, for operation in the fail-safe mode;

FIGS. 10A and 10B—are the detailed cross section views of thearrangement of the second hub piece and the stop plate relative to thepulley in normal operation and fail-safe mode respectively, showing thelocking between the pulley and the second hub piece; and

FIG. 11A—is a cross section view of the decoupler in accordance with theembodiment of FIG. 1A showing the one-way clutch but without the torsionspring.

FIG. 11B—is a cross section view of the decoupler in accordance with theembodiment of FIG. 1B showing the one-way clutch but without the torsionspring.

FIG. 12—is a cross section view of the decoupler in accordance with theembodiment of FIG. 1B showing forces exert by the torsion spring on theaxle hub and by the axle hub on the bearing and the pulley due the fitof the torsion spring on the housing cavity.

DETAILED DESCRIPTION OF THE FIGURES

The present invention relates to a decoupler with free wheel system andvibration damping mechanism, as shown in FIGS. 1 to 11, which can beused for different types of mechanical devices such as the couplingbetween pulleys and alternators in automotive vehicles.

As can be seen most clearly in FIGS. 1A and 2A, the decoupler comprisesa shaft 7 to be driven, an axle hub 30 disposed around a driven shaft 7,a pulley 2 arranged externally to the axle hub 30 responsible fordriving the shaft, at least one mechanical element for journaling andcentering between the shaft 7 and the pulley 2, a torsion spring 3 and aclutch spring 5. The torsion spring 3 is disposed between the outer raceof the axle hub 30 and the inner race of the pulley 2 with a first endoperatively attachable to the pulley 2 and a second end operablyattachable to the axle hub 30.

The clutch spring 5 is disposed radially inward of the torsion spring 3and is frictionally attachable to the axle hub 30 to transmit torque tothe shaft 7. In the embodiment of the invention shown in the figures,the clutch spring 5 is disposed between the outer surface of the shaft 7and the inner surfaces of the axle hub 30, so that it is frictionallyattachable to the inner surfaces of the axle hub 30. However, accordingto another preferred embodiment of the invention not shown, the clutchspring 5 can be disposed between the outer race of the axle hub 30 andthe inner surface of the torsion spring 3, so that it is frictionallyattachable to the outer surfaces of the axle hub 30.

FIG. 3 shows a schematic representation of the invention illustratingthe functional components of the decoupler in a block diagram form insuch a way that the outermost component, the accessory drive belt, isshown to the left, and the components which are being successivelycoupled internally are shown toward the right, ending with the innermostelement, the driven shaft, which can be coupled to an alternator. FIG. 3clearly identifies how this invention is distinguishable from state ofthe art decouplers which comprise a belt-driven pulley with an internaltorsion spring 3. Internal to the torsion spring is disposed a one-wayclutch assembly comprising the axle hub 30 and the clutch spring, whoseinner race performs the torque transmitting engagement with the drivenshaft. The decoupler also has at least one journal element allowingrelative rotation between the shaft 7 and the pulley 2. Preferably, thisjournal element is a bearing 8 and a bushing 1 disposed between theshaft and the drive pulley. The details of these parts, the layout andtheir engagement will be described in more detail below with referencesto FIGS. 1 to 11.

The pulley 2 is the component that provides the input torque that istransmitted to the shaft 7, so that the rotational motion of the pulleydrives the rotation of the shaft. In a preferred embodiment of theinvention, the shaft 7 is an alternator shaft driven by the pulley. Thepulley 2 and the shaft 7 are rotatably coupled, however in view of thedecoupler's operation, the shaft may rotate together with the pulleywhen both are in a coupled stated, or when in the disengaged state, theshaft may rotate at a different and greater speed than the pulley(“overrunning”) or even in a different direction from the pulley. Thepulley 2 has an outer surface provided with grooves for engagement of adrive belt (not shown) coupled to other components of a motor such thatthe belt drives the rotational movement of the pulley 2.

In a preferred embodiment of the invention which can be seen moreclearly in FIG. 2A, the pulley 2 has a portion 21 with greater radialthickness and thus smaller inner diameter, which extends radially inwardtoward the first hub piece 4. It should be noted that the pulley stillwould function without this smaller diameter. A bushing 1 is positionedbetween the portion 21 of the pulley 2 and the outer surface of thefirst hub piece 4. The bushing 1 is responsible for journaling andcentering between the shaft 7, the hub first piece 4 and the pulley 2,thereby allowing rotational movement between the shaft 7 and the pulley2.

The pulley 2 also features a central portion 22 with greater diameterthan the portion 21, thereby forming a side of an internal housingcavity 31, within which is disposed a torsion spring 3. The oppositeside of the housing cavity 31 of the torsion spring 3 is limited in theaxial direction by the second hub piece 6. In the region of transitionbetween the smaller inner diameter of portion 21 and central portion 22of larger inner diameter of the pulley 2, is formed a containment wall23 which closes this side of the housing cavity 31 of the torsionspring, and performs the function of containment of leakage of greaseused to lubricate the torsion spring 3. Containment of the grease isnecessary due to the fact that when the decoupler is in operation, therotation of its components generate centrifugal force which tends topush grease out the decoupler. Due to the position of the containmentwall 23 forming a barrier at one end of the central portion 22 of thepulley, the grease is contained within the volume surrounding torsionspring 3.

An inner surface of the pulley 2 has a stop (not shown), which contactsthe first end of the torsion spring 3 when the pulley rotates,transferring torque to the torsion spring 3. Thus, since the second endof the torsion spring 3 is operatively coupled to the second hub piece6, the pulley 2 transmits its rotating torque to the torsion spring 3,which will, in turn, transmit this torque to the second hub piece 6, andconsequently to the shaft 7, as will be explained later.

As the transmission of torque between the pulley 2 and the torsionspring 3 is by means of a stop applying torque to the first end oftorsion spring 3, there is no need for friction engagement between thetorsion spring and the pulley. Thus, the inner surface of the centralportion 22 of the pulley 2 need not have a high hardness and strength.Consequently, the pulley need not be made of wear resistant and heavymaterials, such as steel or other metals, and does not need to besubjected to surface heat treatment. Thus, the pulley can be made oflightweight and cheaper materials that may be less wear resistant suchas aluminum or polymers.

As mentioned previously and as can be seen in the schematic illustrationof the decoupler according to the invention in FIG. 2A, the clutchspring 5 is located between the inside of hub first and second pieces 4,6 and shaft 7, inside the torsion spring 3, instead of being arrangednext to the inner race of the pulley 2, as in the state of the art.Because of this arrangement used the decoupler according to the presentinvention, torsion spring 3 can be larger and the diameter is limitedonly by the inner race of the central portion 22 of the pulley. Torsionsprings of larger diameter more efficiently perform the function ofdamping the torsional vibrations of the engine and are subject to lowerlevels of stress for a given load, which is one of the advantages of theinvention compared to the prior art.

The pulley also has a second portion 24 which has an inner diametercompatible with the diameter of the bearing 8 so as to be press fit ormounted by other suitable means, allowing relative rotational movementbetween the pulley 2 and the shaft 7.

The axle hub 30 of the decoupler is set between the inner race of thepulley 2 and the outer surface of the shaft 7, and inside the torsionspring 3. The axle hub 30 is provided with a first hub piece 4 and aseparate second hub piece 6, being arranged with a gap between them.

The first hub piece 4 is mounted to convey torque to the shaft 7. Thisfirst hub piece 4 has a section 41 with a smaller inner diameter, whichis fitted by interference or by other means appropriate to the shaft 7,and a portion 42 with larger internal diameter, forming a sort ofcavity, in which is housed a portion of the clutch spring 5, which willbe better described later.

The second hub piece 6 is mounted around the shaft 7 and can rotaterelative to it and may include a journal element on the shaft, such as abushing 1. This second hub piece 6, that in this embodiment is arrangedin the end close to the coupling with the alternator, has a first region61 of larger internal diameter and a second region 62 of smallerinternal diameter, thereby forming a kind of cavity in which is housed aportion of the clutch spring 5 in the region of larger internal diameter61. The hub pieces 4, 6 are arranged in such a way in the decoupler sothat the cavities formed in the second hub piece 6 and the first hubpiece 4 are contiguous to one another, forming a single cavity forhousing the clutch spring 5. Therefore, the inner surfaces of the firsthub piece 4 and the second hub piece 6, at least in their regions oflarger diameter 42, 61 which house the clutch spring 5 must be made of amaterial with high hardness to withstand abrasive friction with clutchspring 5. Preferably these surfaces are made of heat treated steel.

Additionally, the transition zones in the regions of larger diameter 42,61 to the regions of smaller diameter 41, 62 of the first hub piece 4and the second hub piece 6 form containment walls 43, 63 of the cavityhousing the clutch spring, and effectively contain grease leakage causedby centrifugal force, similar to that explained previously with respectto the torsion spring 3. Due to the layout of the containment walls 43,63, grease thrown centrifugal outwards runs into these containment walls43, 63 and is stored within the cavity containing the clutch spring 5.

Moreover, as can be seen in FIGS. 2A, 4A, 4B, and 5, the first and thesecond hub pieces 4, 6 are arranged within the decoupler with a smallgap of distance “e” between them, so that the two hub pieces 4, 6 canrotate with respect to one another. The first and second hub pieces 4, 6each have in their respective sides 45, 65 that face the gap, featuresthat serve to prevent grease leakage due to centrifugal force. FIGS. 4Aand 4B show two versions of coupling ends 45, 65 of hub pieces 4 and 6.In the embodiment shown in FIG. 4A, the end 45 of one of the pieces hasa transverse section in an L shape, and the other end piece 65 has across section shaped like an inverted L, so that the two ends fittogether. This configuration provides a labyrinthine geometry, helpingto reduce grease leakage. In FIG. 4B, the edge 45 of the first hub pieceis slanted at an acute angle and the edge 65 of the other hub piece isalso slanted, forming an obtuse angle with the inner surfacecomplementary to the angle of the edge 45 first piece so that the twoends also fit. In any of the embodiments of the invention, a seal forsealing may be further disposed between the two hub pieces 4, 6 of theaxle hub.

FIG. 4C shows an embodiment of the invention wherein a retainer 70 isarranged in the space between the hub pieces 4, 6. The retainer 70 worksas a seal preventing leakage of lubricant through this space, renderingthe free-wheel system tighter. In the second embodiment shown in FIG.4C, the retainer shows a T-shape cross-section wherein the verticalmember is set in the space between the first and the second hub pieces4, 6 and the horizontal member extends over the external race of thefirst and the second hub pieces 4, 6 circumferentially sealing all thespace between the hub pieces. The retainer may be made, e.g., of Teflonor another suitable material to exert function of sealing. If theretainer 70 is applied to an embodiment of the invention that uses thefail-safe system as described above, it will preferably be made of amaterial that, if compressed, does not prevent the locking between thefirst and the second hub pieces 4, 6. The second hub piece 6 also has aradial wall 64 that extends radially outwardly toward the inner race ofthe pulley 2, in the space formed between the torsion spring 3 and thebearing 8. The second hub piece 6 also has a stop (not shown) on itsaxial face, against which runs into the second end of the torsion spring3 when the pulley 2 rotates. By means of the coupling between thetorsion spring 3 and the stop, there is torque transmission from thetorsion spring 3 to the second hub piece 6, which integrates the freewheel system of the decoupler, and which transmits torque to the shaft7, thereby causing rotational movement of the shaft 7. As explainedpreviously, the torque applied to the torsion spring 3 is derived fromthe rotary movement of the pulley 2 and its coupling with the first endof the torsion spring 3.

The rotary motion of the hub pieces 6, 4 cause frictional engagement ofthe clutch spring 5 with the inner races of the hub pieces 6, 4, therebytransmitting torque to the axle 7 in the same direction of rotation withthe axle hub 30 and pulley, or by allowing decoupling between the shaftand the pulley. In the decoupled condition between the shaft and pulley,the decoupler operates as a free wheel system, allowing the shaft 7 torotate in a different direction from axle hub 30 and pulley 2, or byallowing the shaft 7 to rotate in the same direction but at a different,higher speed than the pulley (overrunning).

The shaft 7 driveable by the pulley 2 already described herein has anfirst end region 71 of larger outer diameter, which is mounted by pressfitting or by other appropriate means, onto the smaller internaldiameter portion 41 of the first hub piece 4. The shaft 7 has also asecond end region 73 of larger external diameter, on which one of thebearing elements, preferably bearing 8, is mounted. In this embodimentof the invention, the bearing is set in the axle end opposed to thecoupling with the alternator. The central portion 72 of the shaft 7 hasa smaller outer diameter than the first and second end region 71, 73 andcorresponds to the location of the clutch spring 5. Thus, the centralregion defines, together with the cavities formed in the first hub piece4 and the second hub piece 6, a housing for the clutch spring 5. In theembodiment of the invention in which the decoupler is used to drive analternator, the shaft 7 has an internal thread at one end for attachmentto the alternator shaft, and a splined profile on its internal surfaceopposite the threaded end so that the assembly can be affixed to thealternator pulley using a special tool.

In a preferred embodiment of the invention, the decoupler furtherincludes a washer 11 which is attached at one end to provide sealingagainst leakage of grease, prevent external contamination and provide abetter finish for the assembly.

FIGS. 1B, 2B and 11B illustrate an alternative second embodiment of theinvention. In this embodiment, the bearing 8 is mounted on the axle sidenear to the end for coupling with the alternator, while the bushing 1 isused as bearing element on the side opposed to the coupling with thealternator. This invention of the bearing elements relative to theembodiment shown in FIGS. 1A, 2A and 11A may be advantageous dependingon the side of the shaft 7 in which the greater load is applied, oncethe bearing 8 may withstand higher loads, thus being preferablypositioned in the critical section of the pulley. A flange 50 is alsomounted on the shaft end 7, next to the bearing 8, with structural meansand/or in order to protect the said bearing.

In this embodiment of the invention, the pulley 2 presents a simplifiedinternal geometry, with inner diameter provided only of small variationsand without a portion of greater thickness. A bearing ring 80 is used asauxiliary bearing element, being coupled on the shaft and pulley sideopposed to the side where the bearing 8 is coupled. The bearing ring 80is mounted with interference fit to the pulley inner race. A bushing 1is mounted between the first hub piece 4 and the bearing ring 80, makingan interference fit on the bearing ring 80, and being able to rotaterelative to the hub piece 4. The bushing 1 is responsible by journalingand centering between the shaft 7, the hub first piece 4 and the pulley2, and also allows rotational movements between the pulley 2 and theshaft 7. The first shaft piece 4 is coupled rotation proof to the shaft7.

According this second embodiment of the invention, instead of beingformed in the pulley 2 inner race, the stopper that hits and transfersrotational torsion to the first torsion spring end 3 may, alternatively,be formed on the bearing ring 80. As the bearing ring 80 istorsion-proof coupled to the pulley 2 inner race, the pulley 2rotational movement also causes a rotation in the bearing ring 80, thattransfers this movements to the torsion spring 3. In this embodiment ofthe invention, the positions of the first hub piece 4 and the second hubpiece 6 are inverted to each other relative to the embodiment shown inthe FIGS. 1A, 2A e 11A. The first hub piece 4 is arranged next to thecoupling side of shaft 7 with the alternator. This modifications do notinterfere the functioning of the decoupler according the invention,being the same herein described before for the embodiments shown inFIGS. 1A, 2A e 11A.

The modifications shown in FIGS. 1B, 2B e 11B prove the flexibility ofassembling the decoupler pieces according to the invention. Theflexibility allows the piece assembly to be adjusted due to theplacement of the pulley which applies the greater load on the decoupler.

Further, the use of a pulley of more simple internal geometry associatedto a bearing ring 80 brings the advantage of making the pulleymanufacturing process easier. The internal components assembly is alsoeasier with this pulley geometry modification, as it makes it easier toarrange the pieces in its interior.

The internal arrangement of the decoupler pieces, according deinvention, also allows reduction of the torsional vibration amplitude bymeans of setting the torsion spring 3 inside its housing cavity 31. FIG.12 schematically shows how this technical effect occurs in theembodiment of the invention shown in FIGS. 1B, 2B e 11B, this effectalso being achieved in an equivalent way in the embodiments of theinvention shown in FIGS. 1A, 2A, 11A.

In order to archive this technical effect, it is necessary that the freelength of torsion spring L0 while relaxed be greater than the axiallength L1 of the torsion spring housing cavity 31. In this embodiment ofthe invention, the housing cavity 31 is limited in the axial directionby the bearing ring 80 and by the radial wall 64 of the second hub piece6.

Thus, when the spring is set inside the cavity 31 is exerts a force F1in the axial direction on the internal surface of the radial wall 64 ofthe second hub piece 6. Due to the force F1, the external surface of theradial wall 64 of the second hub piece 6 engages with a bearing elementinternal face placed at that side of the pulley, in this case, thebearing 8. If the pull has a portion with reduced internal diameter 24in the coupling with bearing 8 region, then the second hub piece 6 pushby the torsion spring 3 also engages a shoulder 28 formed in the pulleyinternal race 2 in this reduced diameter portion 24.

As result of the torsion spring 3 compression over the second hub piece6 with force

F1, when a rotation of the second hub piece 6 relative to the pulleyoccurs, a friction force F_(at) is generated in the radial wall 64contact region of the second hub piece 6 with the bearing 8 and with ashoulder 28 of the pulley internal race 2. This friction force can beset by adjusting the compression of torsion spring 3 inside the housingcavity 31. The energy dissipation of the decoupler by means of thisfriction force F_(at) contributes for the reduction of torsionalvibrations of the decoupler.

The decoupler according to the invention has a fail-safe system,illustrated in FIGS. 5 to 10, that allows the decoupler to continue tooperate for a certain time interval, upon failure or breakage of thetorsion spring or clutch spring. This system comes into operation whenthe torsion spring or the clutch spring is subjected to sufficientexcessive stress to cause breakage of either spring.

According to this embodiment of the invention, the decoupler has a stopwasher 9 disposed between the radial wall 64 of the second hub piece 6and the bearing 8 and which extends in the radial direction toward thepulley 2. The washer is press fit on the shaft 7, preferably in thecentral region 72 of smaller outer diameter, as can be seen in FIGS. 5and 6.

The washer 9 comprises a circular shape with flat sides and a thickness“e”. The washer also has a shoulder 91 in a portion of the face that isin contact with the radial wall 64 of the second hub piece 6. FIG. 9shows the geometry of the face of washer 9 in contact with the radialwall 64, and the shoulder 91 in accordance with a preferred embodimentof the invention. In this design, the washer has a raised portion in onequadrant of its surface, constituting shoulder 91. The elevation has athickness “e” in relation to the rest of its surface, and corresponds toan angular region of 90°. This thickness “e” has the same value as thegap between the first and second hub pieces 4, 6. In the region of theshoulder 91, the washer 9 has a thickness of “2e” which can be betterseen in FIGS. 7A and 7B.

The wall 64 of the second hub piece 6 also has a circular shape withflat sides, a thickness “e”, and a ledge on one radial face that is incontact with the washer 9. FIG. 8 shows the geometry of the face of theradial wall 64 of the second hub piece 6 which makes contact with thewasher, and the cam arrangement 101 in accordance with a preferredembodiment of the invention. FIG. 8 shows that the wall 64 is formedwith a raised portion corresponding to ¼ of its surface, forming ashoulder 101. The shoulder 101 has a thickness “e” in relation to therest of its surface, and corresponds to an angular region of 90°.Therefore, in the region of the shoulder 101, the wall 64 has athickness of “2e” which also can be better seen in FIGS. 7A and 7B.

In this embodiment of the invention, the shoulders 91 and 101 of thewasher 9 and wall 64 represent one quadrant of each of the respectivecircular surfaces, however, in other embodiments of the invention, thesecams can take on other sizes, just so they enable the two pieces to beplaced adjacent to each other without the shoulders overlapping.

In normal operation, the washer 9 and the second hub piece 6 are alignedsuch that the shoulder 91 of the washer 9 is rotated so as not to lineup with the shoulder 101 of the wall 64 of the second hub piece 6. Thatis, the shoulder 91 of the washer 9 lines up with the recessed region inwall 64 of the second hub piece 6, while the shoulder 101 of the wall 64of the second hub piece 6 is lined up with the recessed region of washer9, as can be seen in FIGS. 5 and 7A. Thus, the total axial length of thetwo parts, washer 9 and the second hub piece 6, has a total thickness“3e” as shown in FIG. 5. In this arrangement and during normal operationof the decoupler, the second hub piece 6 and the first hub piece 4 aredisposed with the gap spacing “e” between them, and can rotate freelyrelative to one another, as can also be seen in FIG. 5.

However, in the event of an overload applied to the torsion spring andconsequently the second piece hub 6, these parts are induced to rotatemore than the torsion spring 3 would allow, or more than 270°, causingthe shoulder 101 of the wall 64 of the second hub piece 6 to line upwith the shoulder 91, as shown in FIGS. 6 and 7B. In this case, thedecoupler will operate in the fail-safe mode and the assembly of washer9 and the wall 64 of the second hub piece will have a total thickness of“4e”. In this arrangement, the second hub piece 6 is pushed back by adistance “e”, thus eliminating the clearance between the second hubpiece 6 and the first hub piece 4 as shown in FIG. 6. Consequently, thesecond hub piece 6 and the first hub piece 4 are forced into contactwith each other, thus causing the first and second hub pieces 4, 6 tolock together, and therefore to axle 7 which is solidly connected to thefirst hub piece 4. In this case, the decoupler temporarily operates as asolid pulley, transferring rotational movement to the axle 7, until itcan be replaced. In applications in which the decoupler is used in amotor vehicle, the rigid decoupler pulley continues to function,allowing the alternator to continue being loaded, preventing the vehiclefrom stopping because of discharge of the battery.

The fail-safe system of the present invention should also provide lockup between the second hub piece 6 and the pulley 2, so that thedecoupler may operate as a rigid pulley in case of failure or breakageof the torsion spring 3. For this purpose, the inner race of the pulley2 has a recess 26 in the region between the cavity 31 of the torsionspring and the bearing 8 within which are located washer 9 and the wall64 of the second hub piece 6, as can be seen in FIG. 10A. When thewasher 9 and the wall 64 of the second hub piece 6 are positioned in thenormal operating mode, with a total thickness “3e”, the second hub piece6 can freely rotate within the recess 26. However, when the decoupleroperates in the fail-safe mode, the washer 9 and the wall 64 of thesecond hub piece 6 are engaged because of the overlap between theshoulders 91 and 101, with a total thickness of “4e”, and lock up occurswith the second hub piece 6 in the recess 26 as shown in FIG. 10B, sothat the second hub piece 6 cannot rotate relative to the pulley 2.Whereas in this fail-safe mode, the shaft 7 is locked relative to thefirst hub piece 4, and the second hub piece 6 is locked with respect tothe pulley 2, then the shaft 7 also becomes locked with respect to thepulley 2, effectively making the pulley rigid.

According to a preferred embodiment of the invention, to enable suchlocking from the second hub piece 6 and the pulley 2, the recess 26 hasan internal stop (not shown) which runs into or interferes with the wall64 of the second hub piece 6, locking it rotationally only when theshoulder 91 of the washer 9 overlaps the shoulder 101 of the second hubpiece 6, and the washer 9 and the wall 64 of the second hub piece 6assume a total thickness of “4e”.

The fail-safe system described herein may be used in any type decouplerwith free wheel system, simply by including a pulley 2, engaging a shaft7, hub pieces 30 coupled between inner race of the pulley 2 and theouter surface of shaft 7 having a first hub piece 4 that is rotationallylocked on the shaft 7 and a second hub piece 6 mounted around the shaft7 and can rotate relatively to it, and having a radial wall 64 extendingoutward to the inner race of the pulley 2. The first and second hubpieces 4, 6 should be arranged with a gap between them. The decoupleralso must possess at least one journal element between the shaft 7 andthe pulley 2, and a spring friction clutch 5 attachable to the hubpieces 30 for transmission of torque to the shaft 7.

In addition to these essential characteristics, the decoupler fail-safesystem according to the invention should comprise the washer 9 press fitonto the shaft 7 and extending radially within the pulley 2, contactingwith a face of the wall 64 of the second hub piece 6. The washer 9 musthave a shoulder 91 on its face in contact with the wall 64, and the wall64 must have a shoulder 101 at its face in contact with the washer 9.Normally, the washer 9 and wall 64 will be positioned with the shoulder91 of washer 9 rotated so that it fits into the recess of wall 64. Whenan overload is applied to the second hub piece 6, the shoulder 91 of thewasher 9 overlaps the shoulder 101 of the wall 64, so that the secondhub piece 6 is shifted axially toward the first hub piece 4, and thefirst and second hub pieces 4, 6 are locked by contact between them.

In a preferred embodiment this decoupler with fail-safe system, theshoulder 91 of the washer 9 and the shoulder 101 of wall 64 will eachhave a thickness “e” equal to the gap between the second hub piece 6 andthe first hub piece 4. Additionally, the inner race of the pulley 2 hasa recess 26 in the region of contact with the wall 64 of the second hubpiece 6 and washer 9, the recess having an internal stop, which cancontact the radial wall 64, the second hub piece 6 preventing rotationrelative to the pulley 2, only when the shoulder 91 rotates to overlapthe shoulder 101.

The construction and parts of the decoupler in accordance with theinvention also allow the same decoupler to be used independently aseither a decoupler with free wheel system, such as one-way clutch “OWC”.When the decoupler is used in its full configuration with the torsionspring 3 and clutch spring 5, it operates as an over-running decouplersystem described herein. However, it can be adapted to the simpleroperating mode one way clutch illustrated in FIGS. 11A and 11B by simplyremoving the torsion spring 3 and adding the locking means between thesecond hub piece 6 and the pulley 2, which allows the transmission oftorque between the pulley 2 and the second hub piece 6 when the hubpiece rotates in one direction.

In a preferred embodiment of the invention, to lock between the pulley 2and the second hub piece 6, an internal stop is formed on the inner raceof the pulley 2, which can contact the radial wall 64 of the second hubpiece 6 allowing the transmission of torque to the second hub piece 6when the pulley 2 rotates in one direction.

The decoupler, according the invention, also presents the advantage ofsparing an additional component or system acting as torque limiter toavoid that an excessive torque causes the torsion spring to fail, unlikethe couplers of the state of art.

In the decoupler of the present invention, the torsion spring isarranged between the axle hub and the pulley internal race, in a housingregion, so that the spring fits to the pulley maximum internal diameterwhen it expands. Thus, the pulley maximum internal diameter limits (oravoids) an excessive expansion of the torsion spring, during the applyof an eventually excessive torque that may cause the spring to break.So, no additional component or system is necessary for torque limitingand for avoiding spring breakage, as the pulley structure itself,associated with the spring placement, already provides this effect.

This arrangement of the torsion spring in a housing between the axle huband the pulley inner race also provides an additional advantage ofallowing the torsion spring to have a greater diameter for the samepulley encapsulation.

Having described an example of preferred embodiment of the invention itshould be understood that the scope of the present invention encompassesother possible variations, being limited solely by the terms of theappended claims, including therein all possible equivalents.

The invention claimed is:
 1. A decoupler, comprising: a pulley; a shaftactuated by the pulley, and at least one journal element positionedbetween the shaft and the pulley; a hub having a first hub piece and asecond hub piece, the hub being coupled between an inner surface of thepulley and an outer surface of the shaft, wherein the first hub piece ismounted to the shaft and the second hub piece is rotatably positionedaround the shaft, and the second hub piece has a radial wall extendingradially to the inner surface of the pulley; a torsion spring positionedin a torsion spring housing cavity formed by the inner surface of thepulley and an outer surface of the hub, with one axial side of thetorsion spring housing cavity being limited by the second hub piece,wherein an axial length of the torsion spring housing cavity is smallerthan an axial length of the relaxed, unconstrained torsion spring, andthe torsion spring has a first end operably coupled to the pulley and asecond end operably coupled to the second hub piece; a clutch springpositioned internally to the torsion spring and frictionally coupled toboth the first hub piece and the second hub piece for transmission oftorque to the shaft; wherein the torsion spring exerts an axial force onthe second hub piece, and the second hub piece exerts a friction forceon a journal element of the at least one journal element in case ofrotation of the second hub piece relative to the pulley, providing adampening effect to the decoupler; and wherein the clutch spring isdisposed between the outer surface of the shaft and inner surfaces ofthe first hub piece and the second hub piece and frictionally engageswith the inner surfaces of the first hub piece and the second hub piece.2. The decoupler according to claim 1, wherein a gap is disposed betweenthe first hub piece and the second hub piece.
 3. The decoupler accordingto claim 2, wherein at least one seal member is positioned on the gapbetween the first hub piece and the second hub piece.
 4. The decoupleraccording to claim 2, further comprising: a washer mounted on the shaftand extending radially to the pulley, the washer being arranged incontact with a face of the radial wall of the second hub piece; andwherein the washer has a shoulder on a face of the washer in contactwith the radial wall, and the radial wall has a shoulder on the face ofthe radial wall in contact with the washer; and the radial wall andwasher are positioned so that the shoulder of the washer is angularlydisplaced relative to the shoulder of the radial wall, so that when anoverload is applied to the second hub piece, the shoulder of the washerrotates and overlaps the shoulder of the radial wall, causing the secondhub piece to move toward the first hub piece and the first hub piece andthe second hub piece are locked by interference.
 5. The decoupleraccording to claim 4, wherein the shoulder of the washer and theshoulder of the radial wall each have a thickness substantially equal tothe gap between the second hub piece and the first hub piece.
 6. Thedecoupler according to claim 4, wherein the inner surface of the pulleyhas a recess in the region of contact with the radial wall of the secondhub piece and the washer, the recess having an internal stop which cancontact the radial wall to prevent rotation relative to the pulley whenthe shoulder of the washer overlaps the shoulder of the radial wall. 7.The decoupler according to claim 1, further comprising a bearing ringcoupled to the inner surface of the pulley and a bushing mounted betweenthe first hub piece and the bearing ring.
 8. The decoupler according toclaim 7, wherein the bearing ring has a stopper that engages the firstend of the torsion spring in the occurrence of a relative movement ofthe pulley, and the torsion spring housing cavity which is limited inthe axial direction by the bearing ring and by the second hub piece. 9.The decoupler according to claim 1, wherein the pulley is made of atleast one of a steel material, an aluminum material, and a polymericmaterial.
 10. A vibration dampening decoupler, comprising: a pulley; ashaft actuated by the pulley, and a first bearing and a second bearingpositioned between the shaft and the pulley; a hub having a first hubpiece and a second hub piece, the hub being coupled between an innersurface of the pulley and an outer surface of the shaft, wherein thefirst hub piece is mounted to the shaft and the second hub piece isrotatably positioned around the shaft; a torsion spring positioned in atorsion spring housing cavity formed by the inner surface of the pulleyand an outer surface of the hub, with one axial side of the torsionspring housing cavity being limited by the second hub piece, wherein anaxial length of the torsion spring housing cavity is smaller than anaxial length of the relaxed, unconstrained torsion spring, and thetorsion spring has a first end operably coupled to the pulley and asecond end operably coupled to the second hub piece; a clutch spring isarranged internally to the torsion spring and is frictionally coupled toboth the first hub piece and the second hub piece for transmission oftorque to the shaft; wherein the torsion spring exerts an axial force onthe second hub piece, and the second hub piece exerts a friction forceon at least one of the first bearing and the second bearing in case ofrotation of the second hub piece relative to the pulley, providing adampening effect to the decoupler; wherein: the second hub piece has aportion of larger internal diameter and a portion of smaller internaldiameter, forming a cavity between the portion of larger internaldiameter and the portion of smaller internal diameter; the first hubpiece has a portion which is mounted on the shaft and a portion forminga cavity; the cavity formed in the second hub piece is disposedcontiguously with the cavity formed in the first hub piece; the clutchspring is housed inside the cavities of the second hub piece and thefirst hub piece; and a bearing ring coupled to the inner surface of thepulley and a bushing mounted between the first hub piece and the bearingring, the bearing ring having a stopper that engages the first end ofthe torsion spring in the occurrence of a relative movement of thepulley, and the torsion spring being arranged inside the torsion springhousing cavity which is limited in the axial direction by the bearingring and by the second hub piece.
 11. The decoupler according to claim10, wherein the second hub piece has a radial wall extending radially tothe inner surface of the pulley, and a gap is disposed between the firsthub piece and the second hub piece.
 12. The decoupler according to claim10, wherein the clutch spring is disposed between the outer surface ofthe shaft and inner surfaces of the first hub piece and the second hubpiece and frictionally engaged with the inner surfaces of the first hubpiece and the second hub piece.